1. Field of the Invention
The present disclosure relates to a zoom lens and an image pickup apparatus, such as a video camera, a monitoring camera, a digital still camera, or a broadcasting camera, equipped with the zoom lens.
2. Description of the Related Art
A photographic optical system used in an image pickup apparatus, such as a video camera, a monitoring camera, or a digital still camera, which uses a solid-state image sensor is required to have high optical performance and to be a small-sized zoom lens.
Further, a lens which is bright (has a small F-number (Fno)) at a wide angle of view is required to photograph a wide range and further, perform photographing even at night.
Japanese Patent Application Laid-Open No. 1-216310, Japanese Patent Application Laid-Open No. 11-119101, and Japanese Patent Application Laid-Open No. 2012-048200 discuss a three-unit zoom lens including, in order from an object side to an image side, a first lens unit having negative refractive power, a second lens unit having positive refractive power, and a third lens unit having positive refractive power or a four-unit zoom lens including, in order from an object side to an image side, a first lens unit having negative refractive power, a second lens unit having positive refractive power, a third lens unit having negative refractive power, and a fourth lens unit having positive refractive power.
In a negative-lead type three-unit zoom lens or four-unit zoom lens in which a lens unit located closest to the object side has negative refractive power, it is important to appropriately set a refractive power of each lens unit constituting the zoom lens or a lens configuration of each lens unit, and a movement amount during zooming, in order to acquire brightness (small Fno) at a wide angle of view and acquire high optical performance. In particular, it is important to appropriately set the refractive power of the first lens unit or the refractive power of the second lens unit and further, a balance between the refractive power of the first lens unit and the refractive power of the second lens unit.